The present invention relates generally to a radio antenna and, more specifically, to an internal multi-band antenna for use in a hand-held telecommunication device, such as a personal mobile communication terminal (PMCT).
The development of small antennas for PMCTs has recently received much attention due to size reduction of the handsets, requirements to keep the amount of radio-frequency (RF) power absorbed by a user below a certain level regardless of the handset size, and introduction of multi-mode phones. It would be advantageous, desirable and even necessary to provide internal multi-band antennas to be disposed inside a handset body, and these antennas should be capable of operating in multiple systems such as E-GSM-900 (880 MHz-960 MHz), GSM1800 (1710 MHz-1880 MHz), and PCS1900 (1850 MHz-1990 MHz). Shorted patch antennas, or planar inverted-F antennas (PIFAs), have been used to provide two or more resonance frequencies. For example, Liu et al. (Dual-frequency planar inverted-F antenna, IEEE Transaction on Antennas and Propagation, Vol.45, No.10, October 1997, pp. 1451-1458) discloses a dual-band PIFA; Pankinaho (U.S. Pat. No. 6,140,966) discloses a double-resonance antenna structure for several frequency ranges, which can be used as an internal antenna for a mobile phone; Isohatala et al. (EP 0997 974 A1) discloses a planar antenna having a relatively low specific absorption rate (SAR) value; Liu et al. (Dual-Frequency Planar Inverted-F Antenna, IEEE Transactions on Antennas and Propagation, Vol.45, No. 10, October 1997, pp. 1451-1458) discloses a dual-band antenna element having two connected shorted patches and a single feed; Fayyaz et al. (A novel Dual Band Patch Antenna for GSM, Proceedings IEEE-APS Conference on Antennas and Propagation for Wirless Communications, Waltham, Mass., 1998, pp.156-159) discloses a shorted patch antenna, wherein a length of transmission line is added to one edge of the patch to create two resonant frequencies; and Song et al. (Triple-band planar inverted-F antenna, IEEE Antennas and Propagation International Symposium Digest, Vol.2, Orlando, Fla., Jul. 11-16, 1999, pp.908-911) discloses a triple-band PIFA.
In particular, the antenna, as disclosed in Fayyaz et al., has a quarter wavelength rectangular patch antenna that is shorted on one end and has a resonant frequency f1. A transmission line is added to one edge of the patch that is not parallel to the shorted end of the patch to create two resonant frequencies on either side of f1, while simultaneously removing the resonant frequency f1. In that respect, the antenna of Fayyaz et al. is not tunable.
Today""s standard PMCTs operate at two frequency bands (e.g. E-GMS900/1800 in Europe). It would be desirable to have more universal PMCTs, which can be used in multiple systems around the world. For example, the American cellular systems operate at the 850 MHz frequency range (824-894 MHz). It is advantageous and desirable to provide a multi-band internal radio antenna for use in a PMCT that is tunable to cover the system bands of both the European and American cellular systems.
It is a primary object of the present invention to provide a tunable antenna, such as a tunable patch antenna, operating at one or more radio frequency bands. It is a further object of the present invention to provide a tunable antenna, wherein the bandwidth of one or more of the frequency bands can be increased without deteriorating the performance of the antenna at other frequency bands. The objects can be achieved by providing one or more reactive tuning components to a resonant type antenna, such as a patch antenna, for tuning the resonant frequency or frequencies of the antenna. Preferably, the tuning components include one or more low-loss transmission line sections of suitable length and termination. Alternatively, the tuning components include one or more lumped reactive elements.
According to the first aspect of the present invention, a radio antenna for use in a hand-held telecommunications device has a radiating element having a resonant frequency, a grounding point, and a feed point. The antenna comprises:
a transmission line having a length between a first end and an opposing second end, the second end coupled to the radiating element for providing a frequency shift from the resonant frequency, and
an adjustment means, disposed adjacent to the first end of the transmission line, for adjusting the frequency shift by effectively changing the length of the transmission line.
According to the present invention, the adjustment means may comprise:
an extension line, and
a switching mechanism, operable in a first position and a second position, wherein
when the switching mechanism is operated in the first position, the extension line is electrically coupled to the first end of the transmission line for changing the frequency shift, and
when the switching mechanism is operated in the second position, the transmission line and the extension line are electrically uncoupled.
According to the present invention, the adjustment means may comprise:
a plurality of extension lines, each having a different extension length, and
a switching mechanism, operable in a first position and a second position, wherein
when the switching mechanism is operated in the first position, one of the extension lines is electrically coupled to the first end of the transmission line for changing the frequency shift by a shift amount commensurable with the extension length of the coupled extension line, and
when the switching mechanism is operated in the second position, the transmission line and the extension lines are electrically uncoupled.
According to the present invention, the antenna may have a further radiating element having a further resonant frequency. The antenna may comprise
a further transmission line having a length between a first end and an opposing second end, the second end coupled to the radiating element for providing a further frequency shift from the further resonant frequency, and
an adjustment means is further adapted to adjusting the further frequency shift by effectively changing the length of the further transmission line.
According to the present invention, the adjustment means may also comprise:
one or more further extension lines, and
a further switching mechanism, operable in a first position and a second position, wherein
when the further switching mechanism is operated in the first position, one of the further extension lines is electrically coupled to the first end of the further transmission line for changing the further frequency shift, and
when the switching mechanism is operated in the second position, the further transmission line and the further extension lines are electrically uncoupled.
According to the second aspect of the present invention, a hand-held telecommunications device has a radio antenna having a resonant frequency for communicating with other communication devices, and a chassis with a chassis ground for disposing the radio antenna, wherein the antenna comprises:
a radiating element,
a feed point,
a grounding point connected to the chassis ground,
a transmission line having a length between a first end and an opposing second end, the second end coupled to the radiating element for providing a frequency shift from the resonance frequency, and
an adjustment means, disposed adjacent to the first end of the transmission line, for adjusting the frequency shift by effectively changing the length of the transmission line. The adjustment means may comprise:
one or more extension lines, each having a different extension length, and
a switching mechanism, operable in a first position and a second position, wherein
when the switching mechanism is operated in the first position, one of the extension lines is electrically coupled to the first end of the transmission line for changing the frequency shift by a shift amount commensurable with the extension length of the coupled extension line, and
when the switching mechanism is operated in the second position, the transmission line and the extension lines are electrically uncoupled.
According to the present invention, the antenna may have a further a radiating element having a further resonant frequency. The antenna may comprise
a further transmission line having a length between a first end and an opposing second end, the second end coupled to the radiating element for providing a further frequency shift from the further resonance frequency, and
an adjustment means is further adapted to adjusting the further frequency shift by effectively changing the length of the further transmission line.
According to the third aspect of the present invention, there is provided a method of tuning a radio antenna for use in a hand-held telecommunications device having a chassis ground, wherein the antenna includes a radiating element having a resonant frequency, a grounding point coupled to the chassis ground, and a feed point. The method comprises the steps of:
providing a transmission line having a length coupled to the radiating element for providing a frequency shift from the resonant frequency, and
providing an adjustment means for adjusting the frequency shift by effectively changing the length of the transmission line.
According to the present invention, the adjustment means comprises:
one or more extension lines, each having a different extension length, and
a switching mechanism operable in a first position and a second position, wherein
when the switching mechanism is operated in the first position, one of the extension lines is electrically coupled to the transmission line for changing the frequency shift by a shift amount commensurable with the extension length of the coupled extension line, and
when the switching mechanism is operated in the second position, the transmission line and the extension lines are electrically uncoupled.
According to the present invention, the radio antenna also comprises a further a radiating element having a further resonant frequency, and the method further comprises the steps of:
providing a further transmission line coupled to the radiating element for providing a further frequency shift from the further resonance frequency, and
providing a further adjusting mechanism for adjusting the further frequency shift by effectively changing the length of the further transmission line. The further adjustment means comprises:
one or more further extension lines each having a different extension length, and
a further switching mechanism operable in a first position and a second position, wherein
when the further switching mechanism is operated in the first position, one of the further extension lines is electrically coupled to the further transmission line for changing the further frequency shift by a shifting amount commensurable with the extension length of the coupled further extension line, and
when the switching mechanism is operated in the second position, the further transmission line and the further extension lines are electrically uncoupled.
According to the fourth aspect of the present invention, there is provided a radio antenna for use in a hand-held telecommunications device, said antenna including a radiating element having a resonant frequency, a grounding point and a feed point. The antenna comprises:
a tuning component having a first end and an opposing second end, the second end coupled to the radiating element for providing a frequency shift from the resonant frequency, and
an adjustment means, disposed adjacent to the first end of the tuning component, for adjusting the frequency shift.
According to the present invention, the tuning component comprises a lumped reactive element.
The present invention will become apparent upon reading the description taken in conjunction with FIGS. 1 to 7b.